Let's look at how many franchises Marvel got out of this.
Fantastic Four
Doctor Doom
Silver Surfer
X-Men
X-Factor
X-Force
New Mutants
Alpha Flight
Wolverine
Deadpool
Cable
11 franchises right there.
And one-and-done solo films for Gambit, Storm and X-23.
And one character who Marvel technically owned but couldn't use thanks to legal issues with other characters Fox owned is Darkhawk.
We can also see Captain Marvel fight the Brood, Doctor Doom fight Black Panther and Doctor Strange, Juggernaut fight Spider-Man, Hulk and Doctor Strange, Avengers vs Kang, Guardians in an Annihilation, Annihilation: Conquest and War of Kings trilogy, New Mutants and Valkyrie team-up, Wolverine and Elektra team-up, Spider-Man join the Fantastic Four and GW Brige and Abigail Brand join the cast of AOS.
And add the X-Men to the Marvel U through Secret Wars 1983, Age of Apocalypse, House of M or Secret Wars 2015. I'm partial to the former. Beyonder as the main villain. Brings back/recasts dead MCU characters and explains why we never heard about mutants before all in one film.